Osteoarthritis (OA) is a chronic, degenerative joint disease marked by clinical symptoms and joint tissue deformation that predominantly harms joint cartilage, resulting in discomfort, edema, and stiffness near the joint (Jang, Lee, and Ju, 2021). The knee was known as the biggest synovial joint in humans which is made up of synovium, infrapatellar fat pad, ligaments, and bone components and experiences a lot of use and stress; making it a common location for painful disorders, notably OA (knee osteoarthritis; KOA) (Mora, Przkora, and Cruz-Almeida, 2018). KOA is a degenerative, inflammatory condition that affects knee joint and is accompanied by discomfort, impairment, and a lower quality of life (Vitaloni et al., 2019). Increased inflammatory activity has been associated with pain, eventhough the relationship level vary (Dainese et al., 2021). Almost 85% of OA incidences were correlated with KOA (Vos, T. et al., 2016). The prevalence of KOA among asymptomatic uninjured knees were ranging from 4–14% in less than 40 years age adults and 19–43% in adults aged 40 years and over (Culvenor et al., 2019).

Some conservative intervention options for KOA are exercise therapy, non-steroidal anti-inflammatory drugs (NSAIDs), and low-level anti-inflammatory laser therapy (LLLT). In comparison to standard care after 8 weeks, exercise dramatically reduces pain and enhances function, performance, and quality of life in persons with KOA (Goh et al., 2019) However, exercise therapy may be more beneficial for patients who are younger and are not in the waiting period for joint replacement. NSAIDs are recommended in most clinical treatment guidelines KOA, although the intake of these drugs is associated with adverse effects (Rannou, Pelletier, and Martel-Pelletier, 2016). Although some NSAID doses have been demonstrated to be beneficial for managing pain and function in KOA patients, these treatments are probably not suitable for those who have comorbid conditions or for long-term usage due to the minor increase in the risk of side effects, potentially outweighing their clinical benefits (da Costa et al., 2021).

Low level laser therapy (LLLT) is the electronic level absorption of laser light without the production of heat in the visible to near infrared spectral spectrum (390–1,100 nm) (Mussttaf, Jenkins, and Jha, 2019). LLLT–as a non-invasive treatment–can used for a variety of medical conditions, such as pain relief, wound healing, and mainly inflammation reduction in KOA (Tomazoni et al., 2016; Rayegani et al., 2017; Tomazoni et al., 2017). LLLT exhibited many advantages as a therapy. In conjunction with NSAIDs, LLLT reduces levels of inflammation and metalloproteinase (MP-3 and MP-13) in rats with KOA (Tomazoni et al., 2017). In addition, LLLT significantly effect in lowering the levels of pro-inflammatory cytokine expression (IL-1, IL-6, and TNF-α), myeloperoxidase, and prostaglandin E2 than NSAIDs (Tomazoni et al., 2016; Tomazoni et al., 2017). A study has applied KOA three times per week for 8 weeks to rabbits which showed that LLLT has significantly reduced MP-1 and MP-13 and slowed the loss of collagen II, aggrecan, and transforming growth factor beta; suggesting that the effects of LLLT increase over time (Wang et al., 2014).

Interestingly, major osteoarthritis treatment recommendations do not suggest LLLT. The guidelines of Osteoarthritis Research Society International (2018) underlined that LLLT should not stand alone and be regarded as a key intervention in the management of KOA (Collins, Hart, and Mills, 2019), whereas the European League Against Rheumatism osteoarthritis guidelines did not recommend LLLT as therapy for KOA (Geenen et al., 2018). This can be caused by opposition found in some systematic reviews and conflicting meta-analyses. The earliest study concluded that LLLT didn’t show expected changes to KOA patients in terms of pain intensity, severity of KOA, delayed response, stiffness, and functional outcomes (Huang et al., 2015). Next systematic review and meta-analysis found significant differences in total pain and WOMAC function, stiffness, and total on patients with LLLT compared to placebo (Rayegani et al., 2017). Last, a study in 2019 stated that LLLT significantly decreased pain and disability (Stausholm et al., 2019).

Therefore, this critical opinion aims to interpret the latest findings about the potential LLLT application in KOA and also highlight their implications and strategies in future usage.

Laser therapy is a non-invasive technique that promotes faster healing and tissue restoration while also helping to reduce inflammation and relieve pain because of the photobiomodulatory (PBM) effect that laser irradiation can have on cells and tissues (Dompe et al., 2020). There are various kinds of lasers available, and their applications depend on several factors, including wavelength, energy density, power output, and radiation duration. Cell growth is affected by the photobiomodulatory effect, which is mostly brought on by diode lasers with wavelengths in the red and near-infrared range (630–940 nm) while deeper penetration is achieved by using lasers with wavelengths in the “optical window” (600–1100 nm), which also causes a larger cell-light response (AlGhamdi K.M. et al., 2012). These qualities have been used to treat a variety of illnesses and ailments, including diabetes (Everett, L.A. and Paulus, Y.M., 2021), brain damage (Salehpour, F. et al., 2018), spinal cord damage (Vafei-Nezhad, S. et al., 2020), dermatological issues (Lai, D. et al., 2022), and many dental specialties (Nadhreen, A. et al., 2019). Despite many types of laser therapy, LLLT was preferred for its beneficial and safety aspects.

LLLT uses laser light with low energy or intensity which delivers a very small amount of energy, just enough to stimulate the target system without damaging it (Mussttaff, R.A. et al., 2019). LLLT, commonly referred to as photobiomodulation (PBM), has the ability to promote cell proliferation and improve stem cell differentiation (Figure 1) (Dompe et al., 2020). The absorption of red/near-infrared light energy, a process termed “PBM”, enhances mitochondrial ATP production, cell signaling, and growth factor synthesis, and attenuates oxidative stress (Figure 1) (Glass, G.E., 2021). Moreover, the laser makes the cell membrane hyperpolarized and activates the resynthesis of adenosine triphosphate (ATP), which gives regeneration bioprocesses free energy through hydrolysis (Ivandic, T., 2021). Due to its non-invasive nature and low risk of adverse effects, LLLT offers a distinctive strategy. It is also quite accessible, affordable, and even has the potential to be patient-directed at home (Wickenheisser, V.A. et al., 2019).

Seeing the practicality of LLLT, the LLLT technology has been commercialized and applied widely (Glass, G.E., 2021). However, the method of application of lasers varies, as well as the lack of evidence of laser type, dose distribution studies, and wavelength selection and without further rigorous and standardized research, it would create obstacles to the implementation of the LLLT (Wickenheisser, V.A. et al., 2019; Stausholm, M.B. et al., 2019). This concern remains urgent, highlighting the need for various additional preclinical and clinical studies.

As previously noted above, and following recent evidence-based findings about the use of LLLT technology, the authors argue that LLLT technology is a promising therapeutic modality for KOA. These are the latest publications or findings regarding the use of LLLT technology which are used as the basis for the opinions stated previously.

At the length of 785–904 nm, LLLT can be used as non-pharmaceutical and non-surgical treatment modality for KOA patients by combining it with exercises that result in improvement in WOMAC scores, pain, range of motion, and functional status in KOA patients via photobiomodulation (Figure 1). Through this critical opinion, the authors argue that there is sufficient evidence of LLLT to be further used and commercialized as a therapeutic option for KOA patients. However, there are variability in laser application research methodology and the lack of laser type data, dose range research and wavelength selection, and without further rigorous and standardized research, strong data may create barriers to the implementation of LLLT. Furthermore, by applying the latest technology, the authors hope and encourage that other researchers continue to develop LLLT technology in a portable manner that is easy and practical to use by the community, with protocols to regulate the use of tool based on sufficient clinical evidence.